Currently, to meet a soaring requirement for data service traffic, a large quantity of small cells are deployed densely in some indoor or outdoor hotspot areas. A capacity and coverage of an original macro cell are enhanced by using coverage of a small cell, so as to improve user experience. To ensure normal data transmission between a macro cell and each small cell and between small cells, clock synchronization needs to be implemented between the small cells and between the small cell and the macro cell.
In the prior art, clock synchronization is implemented by means of network listening. Specifically, some small cells or macro cells achieve clock synchronization by using a clock synchronization signal provided by an external synchronization source, and as synchronization source cells, provide a clock synchronization signal for a target cell, so that the target cell also achieves synchronization. The external synchronization source may be, for example, global positioning system (GPS) or wired network clock synchronization. In this process, the synchronization source cell transmits a network listening signal to the target cell, so that the target cell can implement clock synchronization with the synchronization source cell according to the network listening signal. To reduce an effect on user equipment served by the target cell, the target cell may receive, by using different network listening resources, for example, by utilizing a non-unicast region in a multimedia broadcast multicast service single frequency network (MBSFN) subframe or by using a guard period (GP) in a special subframe or by using an uplink subframe or by using a downlink subframe, the network listening signal transmitted by the synchronization source cell. How to generate a network listening signal more efficiently for network listening resources of different types has become an urgent problem to be resolved.